Polyethersulfone/Chromolaena odorata (PES/CO) adsorptive membranes for removal of Congo red from water

The demand for manufacturing and application of dyes and pigments in textile industries is increasing. Almost a quarter of the dyes used are discharged as wastewater and some of them are difficult to treat due to their complex structures. Herein, the adsorption of Congo red dye from aqueous solutions was conducted using natural, low cost, easy available and environmentally friendly materials such as stems from Chromolaena odorata (C. odorata or CO), an alien invasive plant species in Southern Africa. The adsorption of Congo red dye was investigated in a series of batch experiments to study the effect of contact time, initial concentration, and initial pH on adsorption efficiency. PES/CO adsorbent-based membranes were fabricated using the phase inversion method. Fourier transform infrared spectroscopy (FTIR) confirmed that PES/CO membranes had hydrophilic functional groups. Addition of C. odorata in PES significantly decreased the surface charge of the prepared membranes by 93%. Dye adsorption percentages of 92%, 27% and 84% were recorded for the C. odorata particles, PES membranes and hybrid PES/CO membranes at pH 6 respectively. The Langmuir-Frendlich isotherms revealed that the adsorption of Congo red occurred on the heterogeneous surface through formation of a multilayer. The adsorption kinetics model suggested that diffusion was a rate-determining step in the adsorption process.